Latent fingerprint development on porous surfaces

ABSTRACT

The disclosed invention pertains to latent fingerprint development, in general, on absorbent surfaces, and more specifically, to make visible latent finger print images of friction ridge material on porous surfaces thereby facilitating comparison of evidence with known finger print images. The preferred embodiment utilizes a contact dry ninhydrin treatment of porous surfaces which are heated by external electromagnetic radiation, such as that obtained from an ordinary microwave oven, to elicit fingerprint images visible without the need for organic solvents or alternate light sources.

Applicant claims priority from Provisional Patent Application No.62/494,340 Filed on 4 Aug. 2017.

BACKGROUND Field of Invention

This patent discloses a method (Contact Ninhydrin) of using a suitableabsorbent substrate, super-absorbent polymer or other moisture source,and a chemical combination on card stock, containing Ninhydrin andenhancers, to visualize latent fingerprints on the absorbent surfaces(paper). This method utilizes microwave energy in combination with theenumerated components to provide a faster, easier and more reliablemethod than prior wet chemical methods. Further, minimally trained orlay persons can use the proposed method to obtain high quality andeasily observed fingerprints on a variety of absorbent surfaces using noorganic solvents.

Discussion of Prior Art

For many years Ninhydrin has been the reagent of choice forvisualization of latent fingerprints on absorbent surfaces, such aspaper. Acetone was the solvent of choice for Ninhydrin developingsolutions, since Ninhydrin is quite soluble in acetone and one caneasily dissolve more than enough Ninhydrin to make a useful workingsolution. It is currently more common to dissolve the Ninhydrin in anonflammable, chlorofluorohydrocarbon solvent or a hydrocarbon solventwith other additives to help the Ninhydrin dissolve since Ninhydrin issoluble only in polar solvents. The chemical reaction between Ninhydrinand amino acids contained in the fingerprint residue is relatively slowat room temperature. People have tried to accelerate the process bysteaming or heating the substrate with an iron, after it was dipped inthe Ninhydrin solution. There is a disadvantage to this as it frequentlycauses purple color development in the background of the substrate andthereby reducing contrast with the purple color that is formed withfingerprint residue. Therefore although the reaction proceeds morequickly the fingerprints produced may not be as highly visible. Also,polar solvents and sometimes even many nonpolar solvents, will causeproblems for Questioned Document examiners because the solvent that isused for the Ninhydrin will often cause ink, particularly ballpoint penink, to run and one loses clarity in the document.

Although commercial or lab prepared Ninhydrin solutions are available,many fingerprint examiners are not chemists and not comfortable withproper precautions and safety measures in using organic solvents bothpolar and nonpolar. A method called “Dry” or as we now prefer to referto it as “Contact” Ninhydrin has been used for a number of years toavoid the ink running problem. This was done by dipping absorbent piecesof paper in a Ninhydrin solution and then, after the solvent hadevaporated, placing the Ninhydrin paper usually on both sides of aevidence document, since it is not known which side of the substratefingerprints are on, and then placing the combination between twoobjects and placing them under something heavy to promote contact. Thepackage is then allowed to react in the dark, usually for an extendedperiod of time (forty eight hours or more). One must make these dryNinhydrin materials to use with the “dry” Ninhydrin method since, as faras we know, they are not available commercially. There are severaldisadvantages to the “dry” Ninhydrin method as it has been used in thepast.

BRIEF DESCRIPTION OF INVENTION

Our “Contact Ninhydrin” method utilizes a sandwich containing the basiccomponents necessary for Contact Ninhydrin fingerprint development. Thesandwich can have an artist board or other low microwave absorbing rigidboard (5.5×8.5 in) as the bottom of the sandwich. Next a piece of thickfilter paper, next a Ninhydrin treated piece of card stock (60-100 lb.paper) treated with Ninhydrin and additives; next fingerprint substrate(normal copy paper with real or synthetic fingerprint material); nextanother piece of card stock treated with Ninhydrin and additives, nextmoisture source that can be diaper pads, dampened 3 MM filter paper orwhat we call a “DelaQ” moisture package (see below), next the top ofsandwich which can be either another artist board, a piece of rigidpolystyrene foam or other rigid plastic boards with low microwaveabsorbance. The sandwich can be held tightly together with heavy-dutyelastic bands. Rigid, but low microwave absorbing plastic sheets canalso be used as the top or bottom of the sandwich.

The sandwich is placed inside a normal microwave oven set at low ordefrost and micro waved for two to five minutes depending on wattage ofthe oven. The sandwich is removed and allowed to cool for a few minutesbefore being opened and the substrate being examined. If the printsdeveloped appear weak or spotty the sandwich can be reassembled, withthe Ninhydrin sheets each turned over to make contact between thesubstrate and Ninhydrin sheets in a slightly different area and microwaved again.

Notations on Preferred Embodiment

-   1. Sandwich is designed at one half normal letter size (5.5×8.5) to    allow it to fit in a normal home-style microwave oven.-   2. The Ninhydrin treated paper is made by immersing the smooth, card    stock in a volatile polar solvent solution containing: Ninhydrin and    additives until paper is saturated. The card stock is allowed to dry    at room temperature.-   3. If fingerprint substrate is full letter size it can be folded in    half with one Ninhydrin sheets place inside the folded paper and one    inside and outside the folded paper. This will allow all surfaces of    the substrate to be developed. Sheets on each side of folded paper    will develop the outside of the substrate sheet while the sheet    inside will develop inside of the folded sheet.-   4. Moisture source can be either diaper pads that have been dampened    thoroughly and allowed to surface dry. They should contain three to    five grams of water absorbed in the superabsorbent polymer beads,    but feel dry to the touch. They can be stored for a considerable    time in a humidified plastic container without losing the absorbed    water. The moisture can also be provided by using two sheets of    heavy filter paper (3 MM). One dry sheet is placed in contact with    the top Ninhydrin sheet and the other sprayed lightly with water and    place in contact with the dry sheet in the sandwich. The third and    most convenient method is using a portable moisture source DeleQ    moisture packet (see below in “Detailed Description” section)

Benefits Over Prior Art of Proposed Contact Ninhydrin Method

-   1. The proposed “contact” ninhydrin method does not cause the    running of most ballpoint pen inks-   2. The proposed “contact” Ninhydrin method greatly speeds the    Ninhydrin reaction with the amino acids in fingerprints versus the    “dry” Ninhydrin method (less than ten minutes versus at least two    days)-   3. The method does not cause colorization of the substrate    background, which makes for better contrast.-   4. Ninhydrin sheets are easily prepared, stored, quite stable and    readily portable.-   5. The development process is free of any organic solvents.-   6. The Ninhydrin sheets are easily made in batches with a “green”    solvent (ethanol).-   7. The Ninhydrin sheets can be used multiple times.-   8. The Ninhydrin sheets use card stock thickness, preferably 80-100    lb stock, but otherwise normal paper. Enhancers added to the    Ninhydrin sheets are designed to speed the reaction and improve    contact between Ninhydrin sheet and substrate. Enhancers reduce the    “spottiness” of prints produced using the older “dry” Ninhydrin    method-   9. The use of microwave on low power settings heats, but does not    color or otherwise charge the substrate. Ninhydrin sheets may become    colored but still retain their activity to react with fingerprint    material and do not color the substrate even on subsequent usage-   10. Although the “dry” Ninhydrin method has been known for a long    time it is invariably a very much slower reaction than one obtains    when using the “Contact Ninhydrin” method. In fact, the recommended    development period is 48 hours or more in the dark for the “dry”    method-   11. The portable moisture source, “DelaQ packets”, are stable for an    extended period when stored in a high humidity closed container.

DETAILED DESCRIPTION

The major components of the “Contact Ninhydrin” method are the use ofninhydrin sheets with additives, the use of gentle microwave heating,the presents of additives to improve contact between substrate andninhydrin and speed the amino acid ninhydrin reaction and the supplyingof steam for gently heating the reaction without significantly wettingthe substrate.

A cocktail of Ninhydrin, high boiling (non-volatile), polar solvent andacid catalyst is placed on the Ninhydrin sheets by dissolving thedesired mixture of materials in a volatile polar solvent. This solutionis used to saturate the card stock sheets and then the solvent isallowed to evaporate, leaving a dry to the touch piece of paper(Ninhydrin sheet) that can be stored in the dark, at room temperature,for an extended period. These sheets can be used multiple times and workparticularly well in combination with heat and moisture provided by therest of the process. The enhancers added to the ninhydrin sheets add acombination of a layer of highly polar, non-volatile, good solvent forNinhydrin, and a source of hydrogen ions needed for the Ruhemann'sPurple reaction. The enhancers can be liquid polymers, ionic liquids ordeep eutectic liquids.

The necessary heating and water vapor source is well supplied by usingthe active areas of diapers, which contain super-absorbent polymer beadsembedded in cotton. They can be wetted thoroughly and allowed to surfacedry, with the moisture strongly held in the beads. The surface of thepad is dry to the touch, but rapidly releases water vapor when subjectedto microwave energy. This function can also be accomplished using heavyfilter paper. If two sheets are used one dry in contact with theNinhydrin sheet and a second lightly dampened in contact with the filterpaper one can release the desired steam with little direct water contactwith the substrate. The use of the super-absorbent polymer allows one todampen the pad and keep it for an extended period so it can be used forfingerprint development without immediate dampening. The diaper padswill hold their water for weeks if kept in a humidified (wet sponge)plastic container.

We have developed an excellent portable moisture source, “DelaQ” packet,using a deliquescent solid (chemical drying agent). We fold an 8.5×11inch piece of #1 filter paper in half and place a 5.5×8.5 inch piece ofplastic window screen inside. A 4-5 gram portion of finely powdereddeliquescent solid in the anhydrous form (sodium or magnesium sulfatework well) is spread evenly over the piece of screen leaving an aboutthree quarter inch empty area around the three open sides. A bead ofwaterproof liquid glue is laid around the three open sides in the openarea and the package is closed by pressing the sides together. The glueis allowed to set overnight under some weight. When the glue has set,the package is placed in a high humidity area. A plastic container witha dampened sponge works well, and is allowed to absorb moisture. Theinitial hydration takes a day or two, but rehydration after use in themicrowave is faster.

The combination of the above materials with largely microwavetransparent boards to hold the sandwich together tightly with the helpof heavy elastic bands, provides a neat package for activation usingmicrowave energy. The sandwich becomes warm enough to speed theRuhemann's purple reaction without discoloring the substrate. Everythingneeded, except for the microwave oven, can be easily transported and canbe stored at room temperature for an extended period.

A combination of the above materials and the described action schemeallows one to make the “Contact Ninhydrin” method a rapid and convenientmethod for visualizing latent fingerprints on a wide variety ofabsorbent substances. A complete kit of necessary materials for theNinhydrin development of fingerprints on absorbent surfaces can be aboutthe size of a large sized book.

SUMMARY OF DISCLOSED INVENTION & PREFERRED EMBODIMENT

Visualizing latent images left on absorbent surfaces, most commonlypaper, is an important investigative technique used by investigators andfingerprint examiners. For many years a solution of Ninhydrin in acetonewas the reagent of choice for visualizing latent prints on absorbentsurfaces, since Ninhydrin is quite soluble in acetone and one can easilydissolve more than enough Ninhydrin to make a useful working solution.It is currently more common to dissolve the Ninhydrin in a nonflammablesolvent or a hydrocarbon solvent with other additives to help theNinhydrin dissolve since Ninhydrin is most soluble in polar solvents.The chemical reaction between Ninhydrin and amino acids contained in thefingerprint residue is relatively slow at room temperature. People havetried to accelerate the process by steaming or ironing the latentfingerprint substrate after it was dipped in a Ninhydrin solution tomake the reaction go more quickly. There is a disadvantage to this as itfrequently causes purple color development in the background of thesubstrate and thereby reduces contrast with the purple color that isformed when amino acids react with the Ninhydrin solution. Therefore,although the reaction proceeds more quickly the fingerprints visualizedmay not be as highly visible. Polar solvents and also sometimes evenmany nonpolar solvents, will cause problems for Questioned Documentexaminers because the solvent that is used for the Ninhydrin solutionwill often cause ink, particularly ballpoint pen ink, to run and oneloses clarity in the document. Although commercial or lab preparedNinhydrin solutions are available, many investigators and fingerprintexaminers are not chemists and not comfortable with proper precautionsand safety measures when using organic solvents both polar and nonpolar.

A little used method that was called “Dry Ninhydrin” has been known fora number of years to avoid the ink running problem. This was done bydipping pieces of paper in a Ninhydrin solution and then, after dryingthe paper, applying them, usually to both sides of an evidence document,since it is not known which side of the substrate fingerprints are on,and then placing the combination under some weight contact. Thiscombination is then allowed to react in the dark, usually for anextended period of time. One must make these dry Ninhydrin materials touse with the “dry Ninhydrin” method since, as far as we know, they arenot available commercially. This method has never been widely used sinceit is very slow, a minimum of 48 hours is recommended and results arenot as reliable as the solution method. We thought we could improve thismethod by warming or finding a catalyst. Surprisingly, we discoveredthat if in addition to the Ninhydrin sheets we added a diaper pad thathad been dampened to wet the super-absorbent polymer beads in the diaperpad and warm the package, under tension, in a microwave oven oneobtained good color development on the substrate with gently heating inabout five minutes. We have greatly optimized this novel process asdescribed in the claims

Contact Latent Image Visualization Process

What is disclosed is method for rapidly visualizing latent frictionridge images left by contact of skin with an absorbent surface(substrate) comprising the steps of:

-   a.) Forming a package under tension of a sheet of card stock    saturated with a solution of chemicals, in contact on both front and    back of the substrate with the latent image and a Delaq package    which is dry to the touch but will provide moisture upon microwave    heating.-   b) The package is held together between two boards that readily pass    microwave energy and are kept under tension using elastic bands.-   c) The dried card stock contains a chemical that reacts with amino    acids and thereby produces a strong color and also contains a high    boiling liquid that enhances contact between card stock and    substrate and catalyzes the chemical reaction.-   d) The “Delaq” package is formed from a card that has a deliquescent    solid dispersed over its surface and held evenly dispersed over the    surface by a piece of plastic screen or flocking material on the    surface of the card and all enclosed in filter paper or thin cloth    folded over it and sealed with a water resistant glue or an iron-on    fusible material to bind the three open sides. The package is    activated by placing it in a humid atmosphere and allowing it to    absorb moisture and then allowing to surface dry.-   e) The entire package, card stock, substrate, “Delaq” package, front    and back boards and elastic bands, is placed in a microwave oven and    heated for a number of minutes with the oven set on “DEFROST”. When    removed from the oven, it is allowed to cool and then the elastic    bands are removed and the individual items taken apart. Whereby any    latent friction ridge images on the substrate become viewable and    can be easily preserved by photography, scanning or other copying    method.

Disclosed is a method for producing a dried sheet of card stockcontaining chemicals that rapidly, upon warming react with amino acidsin the substrate and produce a strong color and also contains a highboiling liquid that enhances contact between card stock and substrateand catalyzes the chemical reaction. The card stock is prepared by:

-   a) Making a solution by dissolving the color producing chemical and    an additive that is a nonvolatile liquid in quantities designed to    provide rapid reaction between the card stock and substrate when in    contact and warned in the presence of moisture. The solvent for the    solution is a polar, volatile organic solvent.-   b) The card stock is immersed in the solution until saturated with    the solution and then removed and the solvent is allowed to    evaporate at room temperature.-   c) When the card stock has dried, the combination of the reactive    chemical and additive provide a medium that enhances contact between    the substrate sheet and the card stock and allows visualization of    any latent images on the substrate in a short time when subjected to    gentle microwave radiation.

Disclosed herein is a method for producing a dry to the touch package(Delaq) that contains considerable moisture in the crystal structure ofa deliquescent solid that can be released by gentle microwave radiationand can be conveniently recharged with moisture so that it can be usedrepeatedly as a convent moisture source. The package is composed of:

-   a) The package is produced using a piece of filter paper or flocked    card stock that contains a deliquescent solid that is evenly    dispersed over its surface and is enclosed by folding over the paper    or cloth to enclose it an outer layer of paper or thin cloth which    seals the material into a stable package.-   b) The deliquescent solid is held in an evenly dispersed manner by    spreading the finely powdered deliquescent solid evenly over a piece    of plastic screen or by spreading it evenly over the surface of the    flocked side of the card stock.-   c) The package is completed by folding a double sized piece of    filter paper or thin cloth over the card or screen and the sealing    the three open sides with either water resistant glue or, in the    case of the cloth, by using an iron-on cloth adhesive.-   d) This package can be recharged after use by placing it in a    humidor. A simple humidor can be fashioned using an airtight    container (plastic, glass or metal) containing a wet sponge or other    highly absorbent material which is kept from direct contact with the    package by a spacer.

In addition, disclosed is a method for visualizing friction ridgeimpressions on absorbent materials that requires no solvents and usesroom temperature stable materials that can be readily transported towhere ever the substrate materials are and only requires a microwaveoven in addition to the readily transported end boards, developmentcards and Delaq packages.

-   a) The method requires only two active items in addition to the    inert cover boards and elastic bands that hold the sandwich    together.-   b) Both the active items are dry to the touch and stable for months    at room temperature when stored in an envelope.-   c) The necessary materials, other than the microwave oven can be    places in a briefcase sized travel bag and easily transported to    wherever they are needed or stored away for easy access.

The disclosed invention and method produces visualization of frictionridge images without colorization of the background as is commonly thecase when the substrate is dipped in a solution of the color formingchemical or sprayed with such a solution.

-   a) Under the conditions of the contact process, the color forming    reaction appears to be a surface reaction.-   b) After several heating cycles the card stock often takes on some    pink coloration, both the substrate containing the friction ridge    latent image does not color which maximized the contrast between the    image and background of the substrate.

Preferred Embodiment One

-   a) Prepare the activated card stock. Cut card stock (80-100 weight)    into 5.5 by 8.5 inch pieces. Prepare a solution in denatured alcohol    or methyl alcohol by dissolving 4 g of Ninhydrin and 25 g of    polyethylene glycol (Tween 80) in 100 ml of the solvent. Submerge    pieces of card stock in this solution until saturated and then    remove and allow to air dry.-   b) Prepare the Delaq package by spreading powdered anhydrous    Magnesium Sulfate evenly over a 5×8.25 inch piece of plastic screen    that is over the bottom half of an 8.5×11 inch piece of filter    paper. The package is completed by folding the top half of the    filter paper over the bottom half and screen and the sealing the    three open sides with a water-resistant glue. This package should be    placed under some weight until the glue has completely dried.-   c) The end boards are ¼ inch thick and 5.5×8.5 inch rigid    polyethylene sheet.-   d) Prepare a sandwich by placing a sheet of activated card stock on    the plastic board, placing the substrate on the card stock. If the    substrate is larger than 5.5×8.5 inch fold it in half and place an    activated card stock sheet inside the folded substrate. Follow that    with another card stock sheet and make sure that these materials are    in close contact and then place a delaq package over the card stock    and finally cover with the other polyethylene board. This sandwich    is then held tightly together with four rubber bands two on each    side. The sandwich is now ready for microwaving. It is placed in a    microwave oven set to the “defrost mode” and microwaved for about    3.5 minutes. The sandwich is then allowed to cool for at least five    minutes before opening the sandwich and examining the substrate for    any visualized friction ridge images.-   e) The sandwich can contain as many as three different substrates    each with activated card stocks on both sides. The card stocks can    be used at least five times without losing any of its activity and    the Delaq package must be regenerated after use by placing it in a    high humidity chamber and it can be reused many times.

Preferred Embodiment Two

-   a) Prepare the activated card stock. Cut card stock (80-100 weight)    into 5.5 by 8.5 inch pieces. Prepare a solution in methyl alcohol by    dissolving 4 g of Ninhydrin and 25 g of a deep eutectic liquid made    from lactic acid and dextrose in 100 ml of the solvent. Submerge    pieces of card stock in this solution until saturated and then    remove and allow to air dry.-   b) Prepare the Delaq package by spreading powdered anhydrous    Magnesium Sulfate evenly over a 5×8.25 inch piece of flocked card    stock that is over the bottom half of an 8.5×11 inch piece of thin    cotton cloth. The package is completed by folding the top half of    the fabric over the bottom half and then sealing the three open    sides with an iron-on adhesive for bonding cloth. This package    should be placed under some weight until the fused adhesive has    cooled.-   c) The bottom end board is a 5.5×8.5 inch artist board and the top    end board is a 5.5×8.5 inch piece of polystyrene board.-   d) Prepare a sandwich by placing a sheet of activated card stock on    the bottom board, placing the substrate on the card stock. If the    substrate is larger than 5.5×8.5 inch, fold it in half and place an    activated card stock sheet inside the folded substrate. Follow that    with another card stock sheet and make sure that these materials are    in close contact and then place a Delaq package over the card stock    and finally cover with the polystyrene board. This sandwich is then    held tightly together with four rubber bands, two on each side. The    sandwich is now ready for microwaving. It is placed in a microwave    oven set to the “defrost mode” and microwaved for about 3.5 minutes.    The sandwich is then allowed to cool for at least five minutes    before opening the sandwich and examining the substrate for any    visualized friction ridge images.-   e) The sandwich can contain as many as three different substrates    each with activated card stock on both sides. The card stocks can be    used at least five times without losing any of its activity and the    Delaq package must be regenerated after use by placing it in a high    humidity chamber. It can be reused many times.

Preferred Embodiment Three

-   a) Prepare the activated card stock. Cut card stock (80-100 weight)    into 5.5 by 8.5 inch pieces. Prepare a solution in denatured alcohol    by dissolving 4 g of Ninhydrin and 25 g of a deep eutectic liquid    made from lactic acid and dextrose in 100 ml of the solvent.    Submerge pieces if card stock in this solution until saturated and    then remove and allow to air dry.-   b) Prepare the Delaq package by spreading powdered anhydrous    Magnesium Sulfate evenly over a 5×8.25 inch piece of flocked card    stock that is over the bottom half of an 8.5×11 inch piece of thin    cotton cloth. The package is completed by folding the top half of    the fabric over the bottom half and then sealing the three open    sides with an iron-on adhesive for bonding cloth. This package    should be placed under some weight until the fused adhesive has    cooled.-   c) The bottom and top end boards are 5.5×8.5 inch pieces of    polystyrene board.-   d) Prepare a sandwich by placing a sheet of activated card stock on    the bottom board, placing the substrate on the card stock. If the    substrate is larger than 5.5×8.5 inches fold it in half and place an    activated card stock sheet inside the folded substrate. Follow that    with another card stock sheet and make sure that these materials are    in close contact and then place a Delaq package over the card stock    and finally cover with the polystyrene board. At this point another    substrate can be added and topped with an activated card stock    sheet. This sandwich is then held tightly together with four rubber    bands, two on each side. The sandwich is now ready for microwaving.    It is placed in a microwave oven set to the “defrost mode” and    microwaved for about 3.5 minutes. The sandwich is then allowed to    cool for at least five minutes before opening the sandwich and    examining the substrate for any visualized friction ridge images.-   e) The sandwich can contain as many as three or four different    substrate sheets each with activated card stock on both sides. The    activated card stock cards can be used at least five times without    losing any of its activity and the Delaq package must be regenerated    after use by placing it in a high humidity chamber. It can be reused    many times.

Overall Advantages of Contact Latent Image Visualizing

-   A. The contact latent image visualization process described above    greatly speeds the color development versus the classic solvent    based Ninhydrin methods by providing results in less than fifteen    minutes versus at least twenty four hours required by most other    methods.-   B. We have not encountered in a hundred or more samples run any    cases where significant colorization of the substrate background    occurs. This enhances the contrast between the background and the    colorized latent image, which is highly desirable.-   C. The contact latent image method does not require any organic    solvents during the processing of the substrate.-   D. The proposed contact latent image method does not cause the    running of most ballpoint pen inks, which allows normal questioned    document examination.-   E. All the necessary materials, except the microwave oven, can be    easily transported in a container the size of typical briefcase.-   F. Because absorbent surfaces have the advantage of providing usable    fingerprints months or even years after they are deposited, the    contact latent image method, can encourage investigators and    fingerprint examiners, who do not have easy access to a fingerprint    laboratory. This should make latent images on absorbent surfaces    more widely used and thereby assist in the solution of more cases.

DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates “Contact Ninhydrin” developed latent prints on paper.10 indicates a print developed with a finger pressed on the paper once.20 indicates the same print pressed on the paper twice. 30 indicates thesame print pressed on the paper a third time. 40 indicates the sameprint pressed on the paper a fourth time. The dry ninhydrin method iscapable of developing latent prints even if the quantity of finger sweatis minimal.

FIG. 2 is a close up of a typical developed latent print using the dryninhydrin process. The disclosed invention offers the high printresolution required for accurate identification.

FIG. 3 illustrates the artist board pieces that can be used as top andbottom of the final development sandwich. They allow the microwaveenergy to reach the moisture containing portion to provide water vaporand heat the Ninhydrin sheets and substrate.

FIG. 4 depicts a photo of the wet ninhydrin process. The prior artprocess requires knowledge of chemistry, a wet bath to immerse thetarget documents, and a large volume of potentially hazardous andflammable materials. Variations in fluid concentration may adverselyaffect print recovery results. The disclosed dry ninhydrin processobviates or mitigates all these limitations.

FIG. 5 is a photo of PAA bead impregnated fiber as found in ordinarybaby diapers. The PAA or Poly Acrylic Acid stabilized within the fibermatrix absorbs copious amounts of water which can be released as steamupon suitable heating, preferably using microwave energy.

FIG. 6 is the chemical equation for the conversion of an amino acid fromthe fingerprint into the chemical compound Ruhemann's purple, whichprovides the color contrast for visualizing the fingerprint.

FIG. 7 is a photo of the assembled “contact” Ninhydrin sandwich used inthe development process. The target paper (substrate) is in the center,surrounded by ninhydrin sheets, covered by PAA-H20 media, covered byartist and polystyrene boards and secured in place using non-ferrousclamps in the form of elastic bands. Non-ferrous materials are requiredfor use in a microwave oven to mitigate energy diversion and IR losses.

FIG. 8 is a photo of portable moisture packed containing a deliquescentsolid enclosed in a filter paper packet.

FIG. 9 is a photo of developed test sheet stamped with syntheticfingerprint material solution to simulate fingerprint residue and havingwriting with six different ball point pens over the latent stamp images.This is the sheet after it has undergone the “Contact Ninhydrin”development process. It shows that there is no discernable effect of the“contact” Ninhydrin process on the ball point ink.

FIG. 10 shows a developed fingerprint sheet with fairly weaklyvisualized fingerprint images. The print with the asterisk marked imageappears fairly faint.

FIG. 11 shows the marked fingerprint image (FIG. 10 above), magnifiedand digitally processed. The processing was minimal, just centroidoptimized and contrast enhanced. This shows that a fairly faintfingerprint processed with the “Contact Ninhydrin” method can show theeasily identified fingerprint minutiae necessary for an identification.

1. A method for rapidly visualizing latent friction ridge images left bycontact of skin with an absorbent surface (substrate) comprising thesteps of: b) Forming a package under tension of a sheet of card stocksaturated with a solution of chemicals, in contact on both front andback of the substrate with the latent image and a Delaq package which isdry to the touch but will provide moisture upon microwave heating. b)The package is held together between two boards that readily passmicrowave energy and are kept under tension using elastic bands. c) Thedried card stock contains a chemical that reacts with amino acids andthereby produces a strong color and also contains a high boiling liquidthat enhances contact between card stock and substrate and catalyzes thechemical reaction. d) The “Delaq” package is formed from a card that hasa deliquescent solid dispersed over its surface and held evenlydispersed over the surface by a piece of plastic screen or flockingmaterial on the surface of the card and all enclosed in filter paper orthin cloth folded over it and sealed with a water resistant glue or aniron-on fusible material to bind the three oJ)en sides. The package isactivated by placing it in a humid atmosphere and allowing it to absorbmoisture and then allowing to surface dry. e) The entire package, cardstock, substrate, “Delaq” package, front and back boards and elasticbands, is placed in a microwave oven and heated for a number of minuteswith the oven set on uDEFROST”. When removed from the oven, it isallowed to cool and then the elastic bands are removed and theindividual items taken apart. Whereby any latent friction ridge imageson the substrate become viewable and can be easily preserved byphotography, scanning or other copying method.
 2. A method for producinga dried sheet of card stock containing chemicals that rapidly, uponwarming react with amino acids in the substrate and produce a strongcolor and also contains a high boiling liquid that enhances contactbetween card stock and substrate and catalyzes the chemical reaction.The card stock is prepared by: a) Making a solution by dissolving thecolor producing chemical and an additive that is a nonvolatile liquid inquantities designed to provide rapid reaction between the card stock andsubstrate when in contact and warned in the presence of moisture. Thesolvent for the solution is a polar, volatile organic solvent. b) Thecard stock is immersed in the solution until saturated with the solutionand then removed and the solvent is allowed to evaporate at roomtemperature. c) When the card stock has dried, the combination of thereactive chemical and additive provide a medium that enhances contactbetween the substrate sheet and the card stock and allows visualizationof any latent images on the substrate in a short time when subjected togentle microwave radiation.
 3. A method for producing a dry to the touchpackage (Delaq) that contains considerable moisture in the crystalstructure of a deliquescent solid that can be released by gentlemicrowave radiation and can be conveniently recharged with moisture sothat it can be used repeatedly as a convent moisture source. The packageis composed of: a) The package is produced using a piece of filter paperor flocked card stock that contains a deliquescent solid that is evenlydispersed over its surface and is enclosed by folding over the paper orcloth to enclose It an outer layer of paper or thin cloth which seal thematerial into a stable package. b) The deliquescent solid is held in anevenly dispersed manner by spreading the finely powdered deliquescentsolid evenly over a piece of plastic screen or by spreading it evenlyover the surface of the flocked side of the card stock. c) The packageis completed by folding a double sized piece of filter paper or thincloth over the card or screen and the sealing the three open sides witheither water resistant glue or, in the case of the cloth, by using aniron-on cloth adhesive. This package can be recharged after use byplacing it in a humidor. A simple humidor can be fashioned using anair-tight container (plastic, glass or metal) containing a wet sponge orother highly absorbent material which is kept from direct contact withthe package by a spacer.
 4. (canceled)
 5. (canceled)